Phylogenetic analyses of Podaxis specimens from Southern Africa reveal hidden diversity and new insights into associations with termites

Abstract

Although frequently found on mounds of the grass-cutting termite genus Trinervitermes, virtually nothing is known about the natural history of the fungal genus Podaxis (Agaricaceae) nor why it associates with termite mounds. More than 40 species of this secotioid genus have been described since Linnaeus characterised the first species in 1771. However, taxonomic confusion arose when most of these species were reduced to synonymy with Podaxis pistillaris in 1933. Although a few more species have since been described, the vast majority of specimens worldwide are still treated as P. pistillaris. Using 45 fresh and herbarium specimens from Southern Africa, four from North America and one each from Ethiopia, and Kenya, we constructed the first comprehensive phylogeny of the genus. Four of the genotyped specimens were more than 100 y old. With the exception of the type specimen of Podaxis rugospora, all herbarium specimens were labelled as P. pistillaris or Podaxis sp. However, our data shows that the genus contains at least five well-supported clades with significant inter-clade differences in spore length, width and wall thickness, and fruiting body length, supporting that clades likely represent distinct Podaxis species. Certain clades consistently associate with termites while others appear entirely free-living.

The genus Podaxis in arid regions of Mexico: preliminary ITS phylogeny and ethnomycological use

“…RAxML analysis of the ITS dataset produced a single most likely tree (Figure 4). We recovered the same six clades (A, B, C, D, E, and F) that were revealed in Conlon (8424, 8422, 8426, 8425, 8423, 22610 and 27843) are placed in (clade E, sensu Conlon et al 2016), with 95% RAxML boostrap support and grouped together with a sequence of P. pistillaris (GenBank: U85336), which has been reported in previous molecular phylogenetic studies of Agaricales fungi (Johnson 1999;Vellinga 2004), while 11 other MEXU specimens (10805, 5772, 12338, 12808, 5015, 27845, 7217, 27558, 1191, 27557 and 7023) were nested within clade D (sensu Conlon et al 2016); however this clade did not receive significant RAxML bootstrap support. All ITS sequences generated from this study were deposited in the GenBank and accession numbers are provided in Table 1 (KY034673-KY034690).…”

“…(Conlon et al 2016) using the multiple sequence alignment program MUSCLE (Edgar 2004), with default parameters in operation. Leucoprinus was used as an outgroup taxon based on previous studies (Hopple and Vilgalys 1999;Conlon et al 2016). MUSCLE was implemented using the program Seaview v. 4.3.…”

“…material 1); however, molecular phylogenetic analysis of the ITS region of these specimens, along with ITS sequences from a recent study of Podaxis spp. from South Africa (Conlon et al 2016), placed the MEXU specimens into two clades: D and E (Figure 4). Therefore, our analysis indicate there are at least two phylogenetic species of Podaxis in Mexico, and not all species of Podaxis collected from Mexico should be identified as P. pistillaris.…”

“…There have been reports of symbiotic association of Podaxis spp. with termites in Australia (Priest and Lenz 1999;Young et al 2002), Nigeria (Alasoadura 1966), South Africa (Bottomley 1948;Conlon et al 2016), and Bolivia (Rocabado et al 2007). In this context, it is worth to mentioning that in the RBTC (Oaxaca, Mexico) such a symbiotic association with termites has not yet been reported.…”

“…Podaxis has been collected from numerous arid regions around world; approximately 44 species have been described to date (Conlon et al 2016). This genus encompasses a wide range of morphological characters such as variation in color, size and shapes in fruit body morphology, as well as a wide range of spore length, width and wall thickness, and has often been confused with Coprinus comatus (Morse 1933;Morse 1941;Herrera 1950).…”